Hi Michele,
> Are there any software that performs HTTP authentication? In particular, I
> have an server application that resides on a web server, and I want to write a
> non-browser client application that can talk to the server app. I'm concerned
> about how my client app can authenticate with the web server. If there are
> existing software that I can use, that would be great. Otherwise, is it
> difficult to write my own?
Not sure if it's exactly what you're looking for, but have a look at
TrustedWeb at http://www.sse.ie/trustedweb
Gary